The United States National Highway Traffic Safety Administration (NHTSA) requires vehicle manufacturers to equip vehicles with a tire pressure monitoring system (TPMS) to detect when one or more of a vehicle's tires are significantly under inflated. Recommended tire inflation pressures are defined by the vehicle manufacturers and provided to drivers in the form of placards, usually located on the driver's side door. At present, the NHTSA requires the driver of a vehicle to be alerted with a telltale if the tire inflation pressure in one or more of the tires is below the higher of a pressure 25% below the vehicle manufacturer's placard pressure or a specified minimum pressure for the specific type of tire on the vehicle. The required telltale is commonly implemented in the form of a malfunction indicator light in the vehicle's instrument panel.